Yeah this kept popping up and although it told me that the Driver: Virtual PC/Windows CE Emulator was the problem it firstly didn't tell me where it was (i.e. filename) nor how uninstall the damn thing?! (just some useless 'check for solutions online' button).
Finally I tracked it down using Microsoft's (was the excellent Sysinternals) LoadOrder tool and the very handy Autoruns. I tracked it down to: "VPCAppSv Provides application services for Virtual PC. Connectix Corporation c:\windows\system32\drivers\vpcappsv.sys" which turns out to be a black listed driver for WinXP. Nice.
So I just deleted from driver list (under HKLM\System\CurrentControlSet\Services) in Autoruns, then rebooted - and no more warnings ;) Then it can just be deleted.